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Online ISSN 1350-911X Print ISSN 0013-5194

Electronics Letters

Volume 23, Issue 16, 30 July 1987

Volumes & issues:

Volume 23, Issue 16

30 July 1987

Testing of complex gates
Modification of a public-key cryptosystem
Neodymium-doped fluoro-zirconate fibre laser
High-quality factors for a sapphire-loaded superconducting cavity resonator
Picosecond pulse response of a travelling-wave semiconductor laser amplifier
Behaviour of a novel cylindrical glass fibre optical coupler buried in KDP
Characteristics of inhomogeneous coupled cylindrical striplines
Complete and rigorous analysis of electromagnetically coupled transverse microstrip dipole
  • Author(s): P. Lepeltier ; J.M. Floc'h ; J. Citerne
  • Source: Electronics Letters, Volume 23, Issue 16, p. 822 –824
  • DOI:  10.1049/el:19870583
  • Type: Article
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  • p. 822 –824 (3)
    A rigorous and complete analysis of the electromagnetically coupled transverse microstrip dipole is presented. This new feeding process offers an alternative solution, which is especially interesting when it is necessary to excite several dipoles from the same line. The theoretical results are compared to experimental measurements in X-band for the input impedance and the radiation patterns (co- and crosspolarisation).
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Demonstration of high capacity in the LAMBDANET architecture: a multiwavelength optical network
  • Author(s): H. Kobrinski ; R.M. Bulley ; M.S. Goodman ; M.P. Vecchi ; C.A. Brackett ; L. Curtis ; J.L. Gimlett
  • Source: Electronics Letters, Volume 23, Issue 16, p. 824 –826
  • DOI:  10.1049/el:19870584
  • Type: Article
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  • p. 824 –826 (3)
    The letter presents transmission measurements in a multi-wavelength optical network, using 18 channels spaced 2 nm around 1.55 μm. Each channel was modulated at 1.5G bit/s and transmitted through 57.8 km of single-mode optical fibre. Experimental results demonstrate a bandwidth-distance product of l.56 Tbit s−1 km and a point-to-multipoint figure of merit of 21.5 Tbit s−1 km node.
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1.55 μm narrow-linewidth multielectrode DFB laser for coherent FSK transmission
Numerical technique for determining steady-state response of nonlinear circuits to multitone input signals
Approach to modelling of microstrip-microslot applicator
  • Author(s): R. Ledee ; P. Pribetich ; P. Kennis ; M. Chive
  • Source: Electronics Letters, Volume 23, Issue 16, p. 829 –831
  • DOI:  10.1049/el:19870587
  • Type: Article
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  • p. 829 –831 (3)
    Microstrip-slot applicators are used for biomedical applications, but their modelling is not easy. We present an approach which considers this type of structure on a lossy medium as a succession of microstrip lines with tuning septums of different sizes. Using a classical spectral-domain approach (SDA) model, calculations of the resonant frequency have been performed and compared with experimental measurements for different simple structures of microstrip-slot applicators.
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Realisation of integrated-optical absorbers for Ti:LiNbO3
Rician envelope estimation and confidence intervals in low signal/noise levels
Fibre-optic magnetic sensor utilising metal-coated fibre
Radiation characteristics of microstrip arrays with parasitic elements
Comparison between the Jacoby-Kost and Horiguchi-Morita binary two-thirds rate modulation codes
Aryabhata algorithm for polynomials
InGaAsP buried heterostructure laser with 22 GHz bandwidth and high modulation efficiency
Fabrication of a new type of field-effect transistor using neutralisation of shallow donors by atomic hydrogen in n-GaAs (Si)
  • Author(s): E. Constant ; N. Caglio ; J. Chevallier ; J.C. Pesant
  • Source: Electronics Letters, Volume 23, Issue 16, p. 841 –843
  • DOI:  10.1049/el:19870595
  • Type: Article
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  • p. 841 –843 (3)
    We describe a new process for the fabrication of GaAs field-effect transistors. This process is based on the neutralisation of shallow donors by atomic hydrogen diffused into a highly silicon-doped epilayer. This original process should be able to produce field-effect transistors with low access resistances. Better linearity and high breakdown voltage are expected owing to the active impurity gradient present in the hydrogenated layer. The first HFETs (hydrogenated FETs) show very encouraging characteristics. For a gate length of 1.2 μm their typical transconductance is 330 mS/mm and the cutoff frequency is larger than 15 GHz.
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High-power aging tests of 1.3 and 1.5 μm VIPS lasers
  • Author(s): S. Oshiba  and  Y. Kawai
  • Source: Electronics Letters, Volume 23, Issue 16, p. 843 –844
  • DOI:  10.1049/el:19870596
  • Type: Article
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  • p. 843 –844 (2)
    1.3 and 1.5 μm VIPS lasers were tested under high-power aging levels up to 130 mW. The output powers of the lasers were enhanced by AR/HR-coating of facets and optimisation of cavity lengths. Aging power levels were 75% of ?Pmaxand were up to 130mW at 25°C and up to 90 mW at 70°C for 1.3μm VIPS lasers. The median lifetimes were estimated to be 150,000 h at 25°C and 60,000 h at 70°C. For the 1.5μm VIPS lasers, the aging power levels were up to 90 mW at 25°C and up to 50 mW at 70°C. Median lifetimes of about 60,000 h and 45,000 h for 25 and 70°C aging tests, respectively, were achieved.
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Very low-noise HEMTs using a 0.2μm T-gate
Bend losses in GaAs/AlGaAs optical waveguides
Optical frequency shifter using linearly birefringent monomode fibre
  • Author(s): C.N. Pannell ; R.P. Tatam ; J.D.C. Jones ; D.A. Jackson
  • Source: Electronics Letters, Volume 23, Issue 16, p. 847 –848
  • DOI:  10.1049/el:19870599
  • Type: Article
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  • p. 847 –848 (2)
    An optical frequency shifter has been constructed which uses travelling acoustic flexure waves induced on a single linearly birefringent monomode fibre to produce mode coupling between the two orthogonal polarisation eigenmodes. The output of the frequency shifter is examined using a heterodyne interferometer. The measured efficiency was ̃2% at a shift frequency of 491 kHz.
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Guided-wave acousto-optic interaction on proton-exchanged lithium tantalate
  • Author(s): J.F. Duffy* ; S.M. Al-shukri ; R.M. de La Rue
  • Source: Electronics Letters, Volume 23, Issue 16, p. 849 –850
  • DOI:  10.1049/el:19870600
  • Type: Article
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  • p. 849 –850 (2)
    A guided-wave acoustic-optic Bragg cell has been fabricated for the first time, to our knowledge, on lithium tantalate. The waveguide is fabricated by dilute melt proton-exchange, and without electrical tuning a maximum diffraction efficiency of 22% has been demonstrated. In addition, the thermo-optic behaviour of the lithium tantalate waveguide has been shown to be similar to that previously demonstrated on titaniumindiffused and proton-exchange lithium niobate waveguides
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Huygens-type formula for curvature loss from dielectric waveguides in optoelectronics
Helicoidal director for circularly polarised waves
  • Author(s): J. Yamauchi ; G. Imada ; H. Nakano
  • Source: Electronics Letters, Volume 23, Issue 16, p. 851 –853
  • DOI:  10.1049/el:19870602
  • Type: Article
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  • p. 851 –853 (3)
    A new type of director for circularly polarised waves is proposed and its characteristics investigated experimentally. The experiment is performed by using an Archimedean spiral antenna as a broadband exciter. It is revealed that the director composed of a helicoid operates over a frequency range of 1 to 2, which is broader than a conventional helix. It is also found that the gain relative to the spiral antenna shows a maximum value of about 5 dB when the axial length of the director is two wavelengths.
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Electroabsorption in GaAs quantum-well waveguides
  • Author(s): N.K. Dutta  and  N.A. Olsson
  • Source: Electronics Letters, Volume 23, Issue 16, p. 853 –854
  • DOI:  10.1049/el:19870603
  • Type: Article
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  • p. 853 –854 (2)
    The measurement of electroabsorption in GaAs quantum-well waveguide modulators is reported. The absorption of the waveguide modes is ̃20cm1 at −10 V applied bias for photon energies ̃90meV below bandgap. The electro-absorption is polarisation-dependent. The absorption for light polarised along the field (TM mode) is smaller (by a factor of four) than for light polarised normal to the field (TE mode). The principal advantage of quantum-well modulators over regular double-heterostructure modulators is in the strong polarisation-dependent absorption. The electro-absorption effect can be used to produce light amplitude modulators, polarisers and photodetectors.
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Minimisation of mutual coupling effect on null steering by using guard elements
GaAs/AlGaAs ridge waveguide laser monolithically integrated with a photodetector using ion beam etching
Reactive ion etching of GaAs using a mixture of methane and hydrogen
Spatial filtering method of oblique slit for measurement of refractive-index profile of optical-fibre preforms
1.2 Gbit/s optical DPSK heterodyne detection transmission system using monolithic external-cavity DFB LDs
  • Author(s): S. Yamazaki ; S. Murata ; K. Komatsu ; Y. Koizumi ; S. Fujita ; K. Emura
  • Source: Electronics Letters, Volume 23, Issue 16, p. 860 –862
  • DOI:  10.1049/el:19870608
  • Type: Article
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  • p. 860 –862 (3)
    The feasibility of using solitary LDs as light sources for a Gbit/s range optical DPSK heterodyne detection system has been confirmed in 1–2 Gbit/s transmission experiments. With monolithic external-cavity DFB LDs, a receiver sensitivity of — 43dBm and transmission over 152 km have been achieved. With conventional discrete external-cavity LDs, — 45dBm and 170 km have also been achieved.
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New analytical expression for the drain current of short-channel MOS transistors in the triode region
  • Author(s): S. Dimitrijev ; D. Župac ; N. Stojadinović
  • Source: Electronics Letters, Volume 23, Issue 16, p. 862 –864
  • DOI:  10.1049/el:19870609
  • Type: Article
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  • p. 862 –864 (3)
    Neglecting the effects of the source and drain electric fields on the depletion-layer charge, and consequently on the drain current, cannot be justified in short-channel MOS transistors. The existing geometrical approach for analysing this problem, known as a charge-sharing model, gives good agreement with experimental data only if an extremely complex expression for the drain current is used. In the letter the use of Gauss's law as a more general approach to analysis of the fringing field effect has been proposed. Using this approach, a simple expression for the drain current of short-channel MOS transistors, which shows excellent agreement with experimental data, has been derived.
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Graphical technique for crosstalk timing analysis
Low-threshold CW operation of an erbium-doped fibre laser pumped at 807 nm wavelength
Erratum: New classes of complementary signals
Erratum: Fabrication of twin-rectangular-cored fibre couplers
Erratum: Multiplexing of interferometric sensors using phase-generated carrier techniques

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